Erica Foley, a 31-year-old Falmouth resident, substitute teacher, and mother of two young children, said she’s always been drawn to fiction that touches on the dark side.

“When I was younger I particularly liked supernatural suspense stories filled with creatures that lurked in the shadows,’’ she said. “Any plot filled with fur, fangs, or phantoms evoked terror — and I loved it.”

These days, Foley said, she has turned toward crime novels based more on real-life settings and human behavior that is terrifying.

“Reading stories that could have been ripped from the headlines allow us to face our fears vicariously and see that good really can triumph over evil,” she said.

She particularly recommends the novel “Five Days in Summer,” by Katia Lief, a chilling story set on Foley’s beloved Cape Cod.

As the story begins, Emily Parker, wife and mother of three, is making a quick trip to the supermarket while on vacation on the Cape. But she disappears in the middle of a crowded parking lot. Eventually, she’s declared missing, and by chance, retired FBI profiler John Geary hears about the case and offers to help.

Immediately, Geary sees similarities to a cold case in which a murderer committed a ritual killing every seven years. If Geary is correct, before five days are out, Parker will be tortured and forced to witness the death of one of her children. The story then follows the gripping search for the killer.

“What makes this story so disturbing is that one of the most serene and beloved coastal vacation spots becomes the setting of a life-and-death nightmare,’’ Foley said.

We may think this could never happen to us, Foley said, “yet at the same time, any woman will easily be able to imagine herself as the victim.”

She added, “It isn’t very often that I literally have to stop reading a novel and walk away in order to catch my breath and calm my emotions down.”

So why then would Foley choose to read this type of book on a beautiful summer day at the Cape Cod National Seashore?”

Her answer: “As much as ‘Five Days in Summer’ disturbed me as a mother, it also captivated me as a reader. On one hand, I needed to know how it ended and who committed the evil acts. But on the other, I was equally afraid to see how it ended.

“It may sound odd that even though my heart was perpetually racing, my stomach was churning, and I couldn’t breathe, I thoroughly enjoyed the entire experience of reading this novel.”

While on the surface Foley’s feelings may appear contradictory, to a psychologist, they make perfect sense.

There are three main theories that account for why readers purposely subject themselves to frightening material.

■ The first, most widely accepted, theory for researchers is that people are willing to endure the terror in order to enjoy a euphoric sense of relief in the end.

■ The second is that an individual is not actually afraid, but is excited. The brain doesn’t distinguish between a real or imagined threat, and because of a hard-wired “fight or flight” response, adrenaline is released. Some call this an “adrenaline rush.”

■ A newer theory has emerged, based on a 2007 study that indicated people can experience both negative and positive emotions at the same time. In a surprising result, researchers Eduardo Andrade and Joel Cohen found evidence that “the most pleasant moments of a particular event may also be the most fearful.” The way Foley described it, reading “Five Days in Summer” is like riding a roller coaster. “Whether you enjoy the intense feeling of excitement at being on the top, or the cathartic release at the bottom when you have survived . . . it’s all good,” she said. She warned, however, “Just wait until your beach vacation is over before reading the novel, or be prepared to lose a lot of sleep.”